DESCRIPTION: The pursuit of synthetic models for metalloproteins and metalloenzymes has made great strides over the last twenty years. For the most part, there has been more progress with respect to the synthesis of structural model compounds as compared to functional models. We wish to strive toward functional model compounds that possess a high degree of selectivity. The focus of the studies proposed here is the Krebs cycle enzyme aconitase, which contains a 4Fe-4S cluster at its active site. This enzyme is one of an emerging class of iron-sulfur hydratase/dehydratases. We propose to mimic the behavior of aconitase using complexes consisting of 4Fe4S clusters ligated to small (<40 residue) peptides. The approach taken here (targeting "metallopepzymes ") is distinct from several others, all of which may be collectively termed de novo metalloenzyme synthesis. While we are quite interested in the reaction catalyzed by aconitase and wish to learn more about its mechanism using models, we will also make attempts to alter substrate specificity and will examine abiological reactions as well. The specific goals for the project can be divided into the following points: a) Design of 4Fe-4S binding peptides, making use of Atassi's surface simulation technique b) Synthesis of cys-containing peptides in a serial fashion using manual synthesis methods c) Simultaneous synthesis of multiple peptide sequences using manual and automated methods d) 4Fe-4S cluster ligation studies, including determination of binding constants and oligomerization state e) "Self-assembly" of iron-sulfur clusters in polypeptide hosts f) Reactivity survey of synthetic "metallopepzymes" g) Physical characterization/ mechanistic analysis of pepzymes. In some respects, the goal is to achieve enzyme-like properties with molecules that may be thought of as multi-metal Zn finger-like peptide complexes.